J-M-L:
does not generate any warning
Maybe for you, but I set mine to File > Preferences > Compiler warnings > All:
C:\Users\per\AppData\Local\Temp\arduino_modified_sketch_286226\sketch_apr05b.ino: In function 'void setup()':
C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.6.21\cores\arduino/Arduino.h:95:39: warning: comparison is always false due to limited range of data type [-Wtype-limits]
#define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
^
C:\Users\per\AppData\Local\Temp\arduino_modified_sketch_286226\sketch_apr05b.ino:5:7: note: in expansion of macro 'constrain'
a = constrain(a, 0, 250); // THIS IS HOW TO DO THAT
^